MongoDB, Inc. officially supports the following projects: the core
MongoDB database (commonly referred to as the server or the kernel),
ten drivers, and a MongoDB-Hadoop connector. These projects are
open-source and open to your contributions.

MongoDB projects are available on GitHub. The get the latest source
from Github, follow the links to the projects.

Unless you are already very familiar with C++ and the MongoDB database,
or already know that you specifically want to work on the Core Server,
we highly recommend that you start by contributing to one of the
Drivers. Why?

Smaller codebase(s) than the core server.

Each driver has a relatively small codebase. This means it is
easier to get familiar with all the parts and how they work
together. Drivers are individually less complex than the core
server, and they are similar in function to each other.

Fewer requirements to get a pull request approved.

There are fewer moving parts in a driver than the core server, due
to the smaller codebase. This makes it easier for us to tell if
your change is going to break something else, whether that
something else is an existing part of the driver or a planned new
feature.

More likely to be in a language with which you are comfortable.

With drivers for different languages, you’re likely to be
comfortable in at least one of those languages.

Apache License.

Among other things, you do not have to sign the contributor
agreement when contributing to the drivers, which can hold up the
pull request process.